Determine DPI (resolution) used in Acrobat document with API

I'm extracting pages to a JPG image (using the JSObject), however I want to know the Height and Width (in inches) of the Page before I extract it (so I can store it for later use).

I can get the X and Y in pixels, but need to know the DPI of the document.  I know that the standard normally is 72 (so just oPage.GetSize.x / 72 should equal the width in inches), however, I could have sworn I've seen some documents (that I created) with other DPI settings.

Is there a way to determine the current DPI setting of the page/document?

		Dim oDoc As New Acrobat.AcroPDDoc
		Dim oApp As New Acrobat.AcroApp
 
		If oDoc.Open("test.pdf") Then
			Dim oJS As Object = oDoc.GetJSObject()
 
			Dim oPage As Acrobat.AcroPDPage
			oPage = oDoc.AcquirePage(0)
 
			Dim oSize As Object
			oSize = oPage.GetSize
 
' HOW DO I DETERMINE THE DPI IN ORDER TO GET THE SIZE IN INCHES?
 
			MsgBox(oSize.x)
			MsgBox(oSize.y)
 
			oJS.SaveAs("c:\temp\test.jpg", "com.adobe.acrobat.jpeg", True)
			oJS.console.show()
			oJS.console.clear()
		End If
 
		oDoc.Close()

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